Speedometer corrector



1968 c. s. SLAUGHTER SPEEDOMETER CORRECTOR 4 Sheets-Sheet 1 Filed Aug. 2, 1965 INVENTOR ATTORNEYS Jan. 16, 1968 c 5 SLAUGHTER 3,363,484

SPEEDOMETER CORRECTOR 4 Sheets-Sheet 2 Filed Aug. 2, 1965 INVENTOR 1 ATTORNEYS 1968 c. s. SLAUGHTER 3,

SPEEDOMETER CORRECTOR (02mm) GElBdS \VniDV INVENTOR ATTORNEY5 United States Patent 3,363,484 SPEEDOMETER CORRECTOR Clarence S. Slaughter, Grand Rapids, Mich., assignor to Powertronics Company, Grand Rapids, Mich., a partnership Filed Aug. 2, 1965, Ser. No. 476,449 3 Claims. (Cl. 74-800) ABSTRACT OF THE DISCLOSURE A speedometer corrector interposed between speedomete'r cable and speedometer and adjusting to correct speed by selected gear reduction ratio and involving at least one deformable gear acting against a selected corresponding rigid gear in a pancake housing and where the deformation is imparted by a case integrated protuberance.

The present invention is directed to a speedometer corrector and more particularly to a compact face to face elastic motion translating structure interposed between speedometer cable and speedomotor to correct for inaccuracies in the speedometer reading as brought about by changes in tires, gear ratios and wheel sizes, for example, in automotive equipment. More particularly the present invention comprises a simple case in pancake form with axial journalling provision for input and output shafting and in which case a pair of face-to-face gear elements are positioned, at least one of the gear elements being resiliently deformable and deformation means in the case causing selected mesh as between the rigid and resilient gear elements, thereby changing a ratio of movement as between a drive and driven element. The drive connection is in some particulars similar in the concept of operation to the disclosure in US. Letters Patent 2,849,897.

One or all of the gear elements may be replaced by gears of variant mesh characteristics so as to change speeds up or down by a correction factor of approximately percent.

As more and more sports cars are seen the importance of the speedometer accuracy in such cars increases and thus the principal object of the present invention is to provide a simple speed correction device insertable between drive cable and speedometer which is relatively quiet and accurate and which gives a substantially wide range of selected correction as necessary.

In addition the present corrector is designed to provide high efiiciency at low cost using gear elements which may be pressed or cast, as well as cut and wherein the entire reducer element is small, is of light weight, and possesses functional compactness.

Another advantage is that the gear elements may be easily inserted in the units so as to provide any particular correction within the 15 percent range of the device.

In the drawings:

FIGURE 1 is a perspective view of a speedometer corrector in accord with the present invention and indicating its relative position attached to a speedometer shown in phantom line and for coaxial connection at the other side to a speedometer cable shown also in phantom line.

FIGURE 2 is a side elevation view of the present invention as seen in use connected to a speedometer and cable.

FIGURE 3 is a top plan view of the unit seen in FIG- URE 1.

FIGURE 4 is a full cross sectional elevation view taken on the line IVIV of FIGURE 3 and indicating the structure of the present invention connected to a drive cable and prepared for connection to a speedometer.

FIGURE 5 is a cross section elevation view as in FIG- URE 4 of a modified corrector unit utilizing a plurality of resilient gear elements.

FIGURE 6 is a partial cross section elevation view of a solenoid actuated contact pin with spring loaded engagement for selected energization and deenergization of a corrector unit.

FIGURE 7 is a chart of positive and negative corrections available using one and two stage correctors.

FIGURE 8 is a chart showing corrections for snow tires from regular tire sizes.

FIGURE 9 is a chart showing selection of corrector for inaccurate speedometer readings based upon actual timed speed when speedometer reads 60 miles per hour.

FIGURE 10 is a chart showing corrections required for a change in differential ratios.

General description In general the present invention is a speedometer corrector comprising a pancake-like two piece housing, having an axially provided opening therethrough and coaxial journal means in the hub positions extending from the housing or case. Within the housing a cavity is provided for simple resilient mesh face gear means. The gear elements are each secured separately to coaxial shaft elements, one of which is an input shaft and one of which is an output shaft. The gear elements face each other and at least one of the gear elements is resilient. Means are also provided in the case so that the resilient of the gear elements is urged into mesh contact with the rigid one of the gear elements. As the input shaft is rotated the speed of rotation is direct to the gear element secured thereto and as rotation occurs past the point of gear mesh then corresponding rotation occurs in the other of the gears at a differential rate dependent upon the diiferential number of teeth in each of the gear elements and the number of contact points. The input shaft is socketed for connection to a speedometer cable and the output shaft extends to connect with the speedometer. The gear elements may be removed from the case or housing and replaced to provide variants in speed correction. The range of speed correction using a single resilient and a single rigid gear element is approximately 15 percent. However, where larger corrections are necessary a plurality of resilient elements may be used between which a double faced rigid gear element is employed. The resilient gear elements are then urged by separate deforming means into engagement with the rigid gear element. In such a case the rigid intermediate element is journalled coaxially between the resilient gear elements and each of the resilient gear elements are connected to a coaxial shaft, one an input shaft, one an output shaft. In this arrangement, hereinafter called double or 2 phase the correction range is doubled to extend to about 30 percent correction. As in the first form of corrector, the gear elements may be changed as well as contact points.

Specific description By reference to the drawings and with particular reference to FIGURE 1 the speedometer corrector 11 of the present invention is shown intermediate a speedometer 12 shown in phantom line and speedometer drive cable 13. The case 14 of the corrector 11 is in a pancake form and includes a male connector extension 15 and a female connector 16 in coaxial relation to each other and through the center of the case 11. As will be readily appreciated in FIGURE 1, when the cable 13 is disconnected from the speedometer 12, the corrector 11 is inserted therebetween. In FIGURE 2 the corrector 11 is seen thus positioned. In FIGURE 3 the pancake character of the case 14 is appreciated. In FIGURE 4 a full section is seen through the case 14 taken on the axis through the corrector 11. This view reveals the stark simplicity of the structure. The case 14 is seen as a two piece construction wherein the cover plate 17 including the integral male connector 15 closes on the coaxial housing member 18 which includes the integral female connector 16. The cover plate 17 is secured to the housing member 18 on the annular shoulder 19. Securing of the plate 17 may be by welding, brazing, mastic material, thread means or set screws well known in the art and comprising no part of the present invention. Preferably the plate 17 should be selectively removable so that access can be obtained to the cavity 20 formed by the closure of the plate 17 on the housing 18. The plate 17 includes an axial opening 21 defined by the plate 17 and integral male connector extension 15. The opening 21 communicates into the cavity 20 and is coaxial therewith. The housing 18 is similarly arranged with an axial opening 22, therethrough. The opening 22 passes through the integral female connector extension 16, is coaxial with the cavity 219, communicates therewith and is accordingly coaxial with the opening 21. A bushing 23 is provided in the opening 21 providing journal means. A bushing 24 is also provided in the opening 22. The journals thus provided may be integrally formed where desired from the stock of plate 17 and housing 18 respectively. The bushings 23 and 24, respectively, support shafts 25 and 26. Shaft 25 is provided with a drive socket 27 to driveably receive the drive tip 28 secured in coaxial manner to the end of the drive cable 13. This is driveably secured in place by the threaded collar 29 urging the cable 13 into drive relation in the socket 27 of the shaft 25. The shaft 26 is journalled in the bushing 24 and a drive extension 30 is integral with the shaft 26 and extends axially therefrom to engage in the drive socket 31 of the speedometer 12. The engagement occurs when the corrector unit 11 is threaded onto the speedometer 12.

Each of the shafts 25 and 26 include a plate-like face gear element which elements are coaxially oriented in the cavity 20 in operative face-to-face relation. One of the gear elements, for example the gear 32 secured to the shaft 25 is a rigid face gear. The teeth 33 of the rigid gear are provided on a raised tooth annulus 34. The other of the face gear elements, for example gear 35 is driveably secured to the shaft 26 and the face gear 35 is resilient. The teeth 36 of the gear 35 are normally spaced away from contact relation with the teeth 33 of rigid gear 32 and contain a different number of teeth than the gear 32 although the teeth 36 face the teeth 33 for selective engagement, as will be seen. Hence the tooth annulus 37 of the resilient gear is in register with the tooth annulus 34 of the rigid gear.

One or more contact points 38 extend into the cavity 20 to provide deforming contact against the resilient gear 35 at the tooth annulus 37. In FIGURE 1, for example, this is accomplished by the headed pin 39 fixed in the case 14. The degree of contact at point 38 is sufficient to flex the gear 35 into mesh with gear 32 at a point adjacent the head 40 of the pin 39. Accordingly as the shaft 25 rotates in drive relationship from the cable 13 the rigid gear 32 is correspondingly rotated. The effective contact of the rigid gear 32 with the resilient gear 35 is only at those points where contact is urged by the contact point 38. Accordingly the resilient gear 35 is set in motion at a differential rate from the rigid gear 32 and dependent upon the differences in number of teeth in the two gears and the number of contact points 38. As a practical matter adjustment in the corrector 11, shown in FIGURE 1 achieves about 15 percent correction. This correction is established by the selection of particular gears 32 and 35 rated at selected values.

By reference to FIGURE 5, a double or two-phase structure is illustrated. The construction of the twophase corrector 41 involves a case 42 comprising a cover plate 43 and housing 44 which is constructed in a similar manner as the corrector 11. Actually the structure of corrector 42 may be identical in size to corrector 11. A socketed shaft 45 is provided axially through the plate 43 and is suitably journalled therein. A coaxial shaft 46 with speedometer drive extension 47 is journalled in the housing 44 as shown. The shafts 45 and 46 extend into the cavity 48 defined by the plate 43 and housing 44 and are coaxially positioned. Resilient face gear elements 49 and 50 are secured in drive relation to the shafts 45 and 46, respectively. A rigid idler face gear 51 with teeth on both sides is journalled on the stub extension 52 of the shaft 46. The teeth of the rigid idler gear 51 and the resilient face gears 49 and 50 are in registering spaced apart annular relationship and out of contact except as contact points 53 and 54 deform the resilient gears 49 and 50 into meshed relationship as shown. This is accomplished by the headed pins 55 and 56 which extend through the plate 43 and housing 44, respectively and into the cavity 48. It is desirable that the points 53 and 54 be in axial alignment. Plural sets of points 53 and 54 may be used where the axis between them passes through the contact annuli. A slight bevel is desirable in the teeth 57 of the rigid gear 51 correcting for the reformation occurring in the resilient face gears 49 and 50 in achieving mesh contact. Using the structure of FIGURE 5 a variation in number of teeth is available for each gear face and the number of contact points may be varied. From this structure an adjustment or differential in speed as between shaft 45 and 46 can be accomplished up to about 30 percent. Shaft 45 drives gear 49 directly. Gear 4? engages rigid gear 51 by virtue of the contact point 53 thereby imparting motion to the rigid idler gear 51 at a differential rate dependent upon number of teeth in each gear. The idler 51 driven now at the differential rate translates its speed differentially to the gear 50 at contact point 54 thereby imparting motion in shaft 46 at a second differential in speed dependent upon respective numbers of teeth in resilient gear 50 and the corresponding face of the rigid idler gear 51. Hence, a twophase adjustment capable of doubling the correction is available from the structure shown in FIGURE 4.

The gears are all of the face gear type and are easily cast or formed from simple masters without the requirement of expensive cutting or machining. The engagement of the gears is positive without loss in torque or motion and wear excellently. The rigid gear may be for example die cast from a variety of metals and alloys. The resilient gears may be of resin such as known by the trade names nylon or Teflon and a host of other resins having similar strength, resiliency, and memory characteristics. In some instances metals having good flexure and spring characteristics have been used as resilient gears but the forming of the teeth is more difficult. A Wide range of correction is achieved by substitution as required of rigid or resilient gear element-s or both. collaterally and dependent upon the relative differential in tooth number as between adjacent gear elements variant contact points may be provided on the teeth annuli.

By reference to FIGURE 6 engagement or disengagement of contact points 58 serving for example resilient gear 59, is easily accomplished by biasing a pin 60 into contact as by means of a solenoid element of the double acting or single acting type, in the latter instance involving a spring 62 for biasing the pin 60 into a normal or preselected position. The pin 60 in such instances may be provided with an armature extension 63 acted upon by the solenoid coil 61. Such an arrangement is very desirable where variant drive ranges are selected or total disengagement is sought.

In FIGURE 7 a chart is shown indicating in columnated form the positive and negative ratios available from the structures described for speedometer corrections. The FIGURE 8 demonstrates with respect to conversion from regular tires to snow tires the corrections required at various tire sizes for the speedometers. Correction units may then be selected in accord with the positive or negative ratios available in FIGURE 7. FIGURE 9 shows the selection of corrector units as rated by ratio of correction available based upon actual timed speed while speedometer indicated speed shows 60 miles per hour. The FIG- URE 10 is a chart indicating conversions from a known ratio to a selected ratio in accord with available positive and negative corrector units. From these charts the selection of correction factors is made quite simple in utilizing the structures and available ranges of the present invention.

In operation the units built in accord with the present invention are relatively quiet, are inexpensive to construct, are accurate and durable. One of the most unique features of the present invention is to provide a corrector simply coupled betwen speedometer and cable in a compact form with the extensive range of corrections. This results from the unique drive relationship expressed.

Having thus described my invention in an operative embodiment those skilled in the art will readily perceive improvements, changes and modifications. Such improvements, changes and modifications within the skill of the art are intended to be included herein limited only by the scope of the hereinafter appended claims.

I claim:

1. A speed corrector device for connection intermediate a driven shaft and an input shaft comprising:

(a) a pancake housing having axial male and female connector;

(b) at least a pair of coaxial face gears within said housing in face to face spaced relation; and

(c) at least one contact point fixed to said housing flexing at least one of said gears into point contact with the other of said gears at the face thereof.

2. A speedometer corrector for insertion between a speedometer cable and a speedometer comprising:

(a) a two piece housing defining a cavity and an axial connecting passage therethrough with a coaxial male connector at one end and a female coaxial connector at the other end;

(b) an input shaft supported in said housing;

(c) an output shaft coaxially positioned in respect to said input shaft and supported in said housing;

(d) a rigid dn've element secured to one of said shafts for rotation therewith;

(e) a resilient drive element secured to the other of said shafts and in normal spaced apart facing relation to said rigid drive element; and

(f) at least one contact point fixed to said housing flexing said resilient drive element into point contact with said rigid drive element.

3. A corrector for adjusting the speed of rotation of an element such as a speedometer cable and transmitting the adjusted speed to a readout element comprising:

(a) at least one plate-like rigid drive element drivably secured to a first shaft;

(b) at least one plate-like resilient drive element in normal spaced apart parallel relation to said rigid drive;

(c) at least one pressure point flexing said resilient drive element into contact with said rigid drive element;

(d) a second shaft coaxial to said first shaft operably driven by the other of said drive elements;

(e) a first housing element journalling one of said shafts and including a threaded connection; and

(f) a second housing element coaxially positioned and secured to said first housing element, together said housing elements defining a cavity in which said drive elements are positioned and supporting one of said pressure points.

References Cited UNITED STATES PATENTS Re. 22,549 9/ 1944 =P1enser 74800 X 452,490 5/1891 Thomson 74-805 X 1,259,727 3/1918 Weil et al 74805 1,395,193 10/1921 Lindenberg 74805 2,455,284 11/1948 Van Riel 74-805 2,849,897 9/1958 Walma 74-800 X 2,908,191 10/1959 Sundt 74-804 3,258,994 7/1966 Gorfin 74- 804 X 3,262,081 7/1966 Fairbanks 74800 X FOREIGN PATENTS 139,327 9/ 1948 Australia.

683,841 6/1930 France.

249,805 10/ 1926 Great Britain.

218,444 4/1942 Switzerland.

DONLEY J. STOCKING, Primary Examiner. ARTHUR T. MCKEO'N, Examiner. I. R. BENEFIEL, Assistant Examiner. 

